The present invention relates generally to surveying, and more particularly, to a tracer bullet for use in vertical projection surveying. Vertical projection surveying is designed to be used in areas where survey points are not visible from one another such as in hilly terrain or wooded areas. Essentially, it entailes projecting from a hidden survey point to an observable point located vertically above the hidden point.
Three methods have been employed in vertical projection surveying:
The first is the Hoversight Method, developed by the U.S. Geological Survey, which utilizes a flashing target, mounted to a helicopter, and positioned directly above a hidden survey point. This method requires the coordination of the helicopters with ground crews and computers and is obviously quite costly.
The second method is the U.S. Forest Service's Lazer Range Pole which directs a vertical column of light above a hidden survey point. The column is visable through a specially designed theodolite located at a remote survey point. A major drawback of this method is its cost which is currently quoted at approximately $92,000 per unit.
The third method, which utilizes the vertical projection of a trace, is employed with the present invention. This method is described in U.S. Pat. No. 3,350,783 which is hereby incorporated by reference. Utilizing this method, the applicant's tracer bullet is fired vertically and leaves a momentary trace which is viewable from a remote survey point through a surveyor's transit. The tracer bullet is differentiated from military type tracer bullets, the trace from which can only be seen from behind by the person who fired the bullet. The instant tracer bullet also improves over others in that it includes the addition of a desiccant, silica gel kernels, to the gunpowder in the shell. The silica kernels substantially prolong the shelf life of the bullet by binding the moisture within the shell and thereby allowing the oxygen within the pyrotechnic to be available for combustion. The use of the applicant's tracer bullet with the vertical projection method is less costly in equipment and materials, and saves considerable time over other vertical projection survey methods.